Questions tagged [thermodynamics]

Covers the study of (mostly homogeneous) macroscopic systems from a heat/energy/entropy point of view. Consider also using tag: [statistical-mechanics].

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Microscopic explanation of colligative properties from the entropy related viewpoint

In the chapter 28.6 of book "Concepts in thermal physics "(2nd edition) written by Stephen J. Blundell, there is a sentence says "Adding a small quantity of solute to a solvent increases the entropy ...
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Heat definition in isotherm and first principle of thermodinamic

We know that the heat Q can be computed by $Q=cm\Delta T$ and in a phase change by $Q=Lm$ (L latent heat). In isotherm process and with no change of phase we can't use those formulas and there's no ...
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Johnson-Nyquist Noise and the Assumption of a Noiseless Load

I'm a little stuck on a subtlety of RF/microwave design that I find a bit baffling. It has to do with the convention of using of noiseless resistors as loads in circuit noise analysis. I have not yet ...
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A Contradiction in work done or work energy theorem?

Suppose there exists a Force $F$, acting on a body, which is initially having a velocity $v$, in a direction opposite to that of it's motion. Let the point of application of force produce a ...
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Why are solar panels kept tilted?

I have noticed that, in my country India, most of the solar panels are tilted southward at an angle of ${45}^{\circ} .$ Even on buildings with inverted V-shaped roofs, solar panels are still oriented ...
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What is the significance of the height of these verical lines in Thermal Conductivity graph?

The following image is from the Wikipedia Article on Thermal Conductivity: Please click here if you want a good image resolution, as I was unable to upload it here due to "Unsupported Image Format". ...
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What is the relationship between flow work and velocity of gas?

As we know that for open systems, we have energy conservation equation as $$h+\frac{v^2}{2}+zg=const.$$ $$h=u+pV$$ $$u+pV+\frac{v^2}{2}+zg=const.$$ Here $pV$ is flow energy. We know that all these ...
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Feynman Lectures Vol I 41-2: why can $\omega$ replace $\omega_{0}$ in deriving Rayleigh’s law?

NB: I understand that the model presented here is the "failing" classical model. I'm just trying to understand the formal reasoning of the model. In The Feynman Lectures on Physics Vol. I Ch. 41-2 ...
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How to express $k_BT$ as a length scale?

I am wondering how we can use $k_BT$ to define a length scale? I mean it is a unit of energy, not of length. So how would that transformation work?
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Why does a black hole have much entropy?

Is that just an assumption by Bekenstein etc? For example, what is the different states a non-rotating primordial black hole can be in?
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Why should $E$ and $B$ both contribute $(1/2) kT$ in equilibrium radiation?

At high temperatures/low frequency, energy distributes itself by equipartition. There's a factor of $\frac{1}{2}kT$ for each degree of freedom that contributes quadratically to the energy. So, for ...
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What is the temperature at which water will boil at an altitude where pressure drops by 10%? [on hold]

If there is a 10% decrease in the atmospheric pressure at a hill compared to the pressure at sea level, then the change in the boiling point of water is_____ °C. (Take latent heat of vaporisation of ...
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How can saturated steam be in vapor-liquid equilibrium if all water has evaporated?

I'm reading Saturated steam on Wikipedia. It is said: ... water vapor that includes water droplets is described as wet steam. If wet steam is heated further, the droplets evaporate, and at a high ...
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Vaporizing water by piston work

Consider you have an adiabatic container with a piston. At the moment, the the container has liquid water and air, of known mass, in the headspace at 1 bar and 298 K. Suppose I perform some PV work by ...
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Derivation of temperature / entropy relation from statistical mechanics

I am trying to prove that \begin{equation} \frac{1}{T} := k_B\beta = \frac{\partial S}{\partial E}. \end{equation} I have that \begin{equation} E := \sum p_i E_i, \end{equation} the Gibbs entropy \...
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How to find volume from pressure, mass flow rate, and burn time?

I must find the minimum volume needed for two tanks, one with liquid oxygen (LOx) and one with liquified natural gas (LNG), knowing only the mass flow rate of each, and the burn time of the engines. ...
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How air pressure depend upon the rate of evaporation? [on hold]

I think these are inversly proportional to each other if not so please explain me
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Is the kinetic theory of gas relative in nature

In kinetic theory of gas the foremost assumption is that the temperature of an object is due to the kinetic energy of the atoms/molecules contained in it. But as we know that kinetic energy is a ...
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How to calculate work for irreversible adiabatic processes?

By the first law, we know $\text{d}U=\delta Q+\delta W$ and, on adiabats, we know $\text{d} U=\delta W$. But what is $\delta W$ for irreversible adiabatic processes? Take a thermally isolated ...
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What is the best way to move air in a room that has several computers? [on hold]

I have a computer room that is $12$' by $20$' in size and holds two large computer systems that generate a lot of heat. The room has a regular $2.5$ ton AC unit and I have a $12,00$ BTU window unit ...
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Can the sound change the state of the medium?

The waves perform compression and rarefraccion in the medium where they spread, right?   when the rarefraction happens we should feel the medium in a liquid or gaseous state since the molecules ...
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How to formulate surface temperature of a material exposed to sunlight and wind?

I am currently searching for a model or an approach (reference, course, demonstration) to formulate and estimate surface temperature of a known material (for example, concrete, metal), exposed to ...
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What quantity remains conserved in a calorimeter when two bodies at different temperatures are mixed?

This is the question: Two identical bodies at different temperatures are mixed in a calorimeter. Which of the following quantities remains conserved? 1) Sum of the temperatures of the two bodies 2) ...
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If $\mathrm df$ is an inexact differential, how would the function $f$ look like?

I am studying thermodynamics and in the first chapter the concept of exact and inexact differentials were used to talk about the differences between internal energy, work and heat. From Blundell and ...
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Reversible engines

As far as my understanding goes, the only reversible heat engine is the Carnot engine, described by the Carnot cycle. On the other hand, in all of the resources I've found the change in entropy for ...